An Efficient Causal Protocol with Forward Error Correction for Mobile Distributed Systems

Problem statement: Causal ordering is used in Mobile Distributed Systems (MDS) to reduce the non-determinism induced by four main aspects: host mobility, asynchronous execution, unpredictable communication delays and unreliable communication channels. Some causal protocols have been proposed for MDS. All of these protocols in order to ensure the causal order in unreliable channels use the method of Automatic Repeat Request (ARQ). They detect a lost message and carry out the retransmission of this message. This approach was not recommended in a real time mobile distributed system because it increased the transmission delay of the data and the overhead sent in the communication channels. Approach: In this study, we proposed a protocol that ensured the causal order of messages in unreliable and asynchronous MDS. In our protocol, the detection and recovery of lost messages was achieved by the method of Forward Error Correction (FEC) in a distributed form. One interesting aspect of our Causal-FEC protocol was that the redundant information sent in the wired and wireless communication channels is dynamically adapted to the behavior of the system. Results: Our protocol was efficient in terms of the overhead attached per message, the computational cost and the storage control information at a mobile host. Conclusion: The present study is one of the first works on causal algorithms based on forward error recovery in mobile networks.